Hydronic surface heating system

ABSTRACT

A mobile surface heater is disclosed having a heat generation loop and a heat dissipation loop. The heat generation loop can include a heat generating device, a storage tank, and a first pump for circulating a fluid. The heat dissipation loop can be placed in fluid communication with the heat generation loop and includes a ground heating system having at least one heat transfer conduit extending between a supply manifold and a return manifold. A control valve can also be provided to deliver a mixed fluid flow stream to the ground heating system by selectively mixing fluid from the heat generation loop with fluid returning from the ground heating system return manifold. In one embodiment, an electronic controller is provided that operates the mixing valve to maintain a temperature setpoint of the mixed fluid flow stream and to maintain a minimum entering fluid temperature setpoint of the atmospheric water heater.

BACKGROUND

A mobile ground surface heater refers to a piece of portable equipment that is transferred from location to location for different heat transfer applications. Mobile ground surface heaters are used in a variety of situations, including indoor and outdoor construction, ground thawing for excavation, frost prevention, concrete curing, air heating, freeze protection, etc. In some embodiments, mobile ground surface heaters utilize hydronic heating principals. Hydronic heating is the use of water as the heat-transfer medium in heating systems. Improvements in hydronic mobile ground surface heaters are desired.

SUMMARY

A mobile ground surface heater is disclosed having a heat generation loop and a heat dissipation loop. The heat generation loop can include a heat generating device such as an atmospheric water heater, a storage tank, and a first pump for circulating a fluid, such as water, glycol or a water-glycol mixture, through the heater and tank. The heat dissipation loop can be placed in fluid communication with the heat generation loop and includes a ground heating system having at least one heat transfer conduit extending between a supply manifold and a return manifold. The heat dissipation loop may also include a second pump configured to circulate fluid through the heat dissipation loop. A control valve can also be provided to deliver a mixed fluid flow stream to the ground heating system by selectively mixing fluid from the heat generation loop with fluid returning from the ground heating system return manifold. In one embodiment, an electronic controller is provided that operates the mixing valve to maintain a temperature setpoint of the mixed fluid flow stream and to maintain a minimum entering fluid temperature setpoint of the heat generating device. The mobile ground surface heater also includes a chassis having at least one pair of wheels that is configured to support the aforementioned components of the heat generation and dissipation loops.

A method for operating a ground surface heater is also described. In one step of the method, a ground surface heater having a heat generation piping loop and a heat dissipation piping loop are provided wherein the heat dissipation loop includes at least one heat transfer conduit. In another step, a control valve is provided to provide a mixed flow to the heat transfer conduit by mixing heated fluid from the heat generation piping loop with return fluid from the heat transfer conduit. In another step, the control valve operates to maintain a heat generation loop minimum temperature setpoint. In another step, the control valve operates to maintain a heat dissipation loop temperature setpoint. In one configuration, the system gives priority to the heat generation loop minimum temperature setpoint over the heat dissipation loop temperature setpoint. In one configuration, the system monitors a ground temperature setpoint and enters a maintenance mode once the setpoint is achieved. A user notification may also be generated and sent once the ground temperature setpoint has been reached.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting and non-exhaustive embodiments are described with reference to the following figures, which are not necessarily drawn to scale, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified.

FIG. 1 is a schematic view of a hydronic heating system for a mobile ground surface heater having features that are examples of aspects in accordance with the principles of the present disclosure.

FIG. 2 is a schematic view of the hydronic heating system of FIG. 1 in a non-mixing mode of operation.

FIG. 3 is a schematic view of the hydronic heating system of FIG. 1 in a mixing mode of operation.

FIG. 4 is a schematic view of a control system for the hydronic heating system shown FIG. 1.

FIG. 5 is a front perspective view of a mobile ground surface heater using the hydronic heating system shown in FIG. 1.

FIG. 6 is a rear perspective view of the mobile ground surface heater shown in FIG. 5.

FIG. 7 is a first side view of the mobile ground surface heater shown in FIG. 5.

FIG. 8 is a second side view of the mobile ground surface heater shown in FIG. 5.

FIG. 9 is a flow chart showing a process for operating the mobile ground surface heater shown in FIG. 5.

FIG. 10 is a flow chart showing a process for controlling the mixing valve of the mobile ground surface heater shown in FIG. 5.

FIG. 11 is a flow chart showing a process for monitoring ground surface temperature using the mobile ground surface heater shown in FIG. 5.

DETAILED DESCRIPTION

Various embodiments will be described in detail with reference to the drawings, wherein like reference numerals represent like parts and assemblies throughout the several views. Reference to various embodiments does not limit the scope of the claims attached hereto. Additionally, any examples set forth in this specification are not intended to be limiting and merely set forth some of the many possible embodiments for the appended claims.

Hydronic System

Referring to FIG. 1, a schematic for a hydronic heating system 100 is shown. The hydronic heating system 100 is for heating a fluid stream that can be used to heat a ground surface 12, and is part of a mobile ground surface heater 10. The fluid stream may be any fluid capable of transferring heat, such as water, ethylene glycol, propylene glycol, and mixtures thereof. As shown, hydronic heating system 100 has two defined hydronic circuits that interface with a mixing control valve 106: a heat generation loop 102 and a heat dissipation loop 104. The heat generation loop 102 operates to heat the fluid stream while the heat dissipation loop 104 operates to transfer the heat to the ground surface 12. The mixing control valve 106, as discussed in greater detail later, operates to control the fluid temperature in the heat dissipation loop 104 while ensuring that the heat generation loop 102 is maintained at a sufficient temperature for proper operation of the hydronic heating system 100.

As shown, the heat generation loop 102 includes a heat generating device 108. The heat generating device 108 may be any type of device capable of heating the fluid stream. Non-limiting examples of heat generating devices 108 suitable for use with the hydronic heating system 100 are boilers and water heaters. In the embodiment shown, the heat generating device 108 is an atmospheric water heater having a diesel fired burner 112 that draws fuel from a fuel tank of the fuel delivery system 134. It is noted that heat generating device 108 could utilize a burner 112 that relies upon another type of fuel, such as propane, natural gas, or gasoline, and also that an electric type heating element may be utilized instead of a burner 112. As configured, the burner 112 heats fluid contained in a vessel 114 in the heat generating device 108 which is provided with a pressure relief valve 116. The pressure relief valve 116 operates to ensure that the rated vessel pressure is not exceeded, for example when high pressures are caused by fluid or water flashing from excessive temperatures.

The heat generation loop also includes a fluid storage tank 110. The fluid storage tank 110 is for increasing system fluid volume for more even loading of the heat generating device 108, and also operates to allow the fluid to reside at a low velocity such that any entrained air in the system may be removed. The fluid storage tank 110 is provided with a vent 120 for this latter purpose. The increased volume from the fluid storage tank 110 also allows the heat generating device 108 to heat a sufficient volume of fluid during the warm-up phase before sending water out to the heat dissipation loop 104 which will initially send unheated water back to the heat generation loop 102 just after mixing between the loops 102, 104 commences.

The heat generation loop is further provided with a first circulation pump 122. The first circulation pump 122 is provided to circulate fluid through the heat generation loop 102, and thus between the heat generating device 108 and the fluid storage tank 110. As shown, first circulation pump 122 is an in-line centrifugal pump, although other types of pumps may be equally suitable. As shown, the first circulation pump 122 is located on the downstream side of the heat generating device 108 such that the pressure in the vessel 114 is not increased by the operation of the pump 122.

The heat generation loop 102 can further comprise a number of piping sections to form a continuous fluid loop with the heat generating device 108, the fluid storage tank 110, and the pump 122. For example, piping section 124 places the pump 122 and the heat generating device 108 in fluid communication with each other while piping sections 126, 128, and 130 place the pump 122 in fluid communication with the fluid storage tank 110. A further piping section 132 places the fluid storage tank 110 in fluid communication with the heat generating device 108. It is noted that the piping sections may be formed of any type of suitable piping, tubing, hosing, and/or conduits compatible with the composition and temperatures of the heat transfer fluid. It is noted that where an atmospheric boiler is used and the storage tank is located vertically higher than the atmospheric boiler inlet, fluid may flow from the fluid storage tank 110 to heat generating device 108 via gravity.

As shown, the heat dissipation loop 104 includes a ground surface heating system 136. The ground surface heating system 136 is for transferring heat from the heat transfer fluid to the ground or other surface 12. In one embodiment, the ground surface heating system 136 includes a supply manifold 138 and a return manifold 140 between which a plurality of flexible conduits 142 may be connected via hydraulic quick connect couplings 144. The flexible conduits 142 extend from the supply and return manifolds 138, 140 and rest on the ground or other surface 12 such that heat from the conduits 142 can be transferred to the surface to be heated 12. In the embodiment shown, manifolds 138, 140 are each provided with connections that allow for up to six conduits to be simultaneously attached.

As quick disconnect couplings are utilized, anywhere between one and six conduits may be attached for any given application. The quick disconnects also allow for the fluid within the conduits 142 to be retained such that subsequent refilling is not required. It is noted that more or fewer than six connection points may be provided at manifolds 138, 140. In order to prevent over-pressurization of the system that may result in too little fluid flow for the connected equipment, a bypass valve 148 may be provided between the manifolds 138, 140 such that a maximum pressure is not exceeded at the supply manifold.

The heat dissipation loop 104 is also provided with a second circulating pump 146. The second circulating pump 146 is provided to circulate fluid through the heat dissipation loop 104, and thus between the ground surface heating system 136 and the heat generation loop 102. As shown, first circulation pump 122 is an in-line centrifugal pump, although other types of pumps may be equally suitable.

As stated previously, a mixing control valve 106 is provided in the system and is located within the heat dissipation loop 104. As shown, mixing control valve 106 is a fully modulating three-way control valve, which may include two separate valve bodies and actuators or a single valve body and actuator. The mixing control valve 106 receives fluid from the heat generation loop 102 via pipe section 150 and receives fluid from the return manifold 140 via pipe sections 156 and 160. The fluid leaving the mixing control valve 106 is delivered to the supply manifold 138 via pipe sections 152 and 154 and circulating pump 146. Any fluid from the return manifold 140 not needed at the mixing control valve 106, which is equal to the fluid flowing into the mixing control valve 106 through pipe section 150, is returned into the heat generation loop 102 via pipe section 158. It is noted that the connection of pipe section 158 to the heat generation loop 102 is located downstream with respect to pipe section 150 to ensure that fluid delivered to the mixing control valve 106 via pipe section 150 is not undesirably reduced in temperature.

As configured, the mixing control valve 106 operates to selectively provide a fluid flow stream to the supply manifold 138 that can be 100% fluid from the heat generation loop 102, 100% fluid from the return manifold 140, or a mixed fluid flow stream comprising any ratio of fluid from the heat generation loop 102 and fluid from the return manifold 140.

Referring to FIG. 2, the hydronic system is shown as being in a non-mixing configuration wherein the mixing control valve 106 is completely closed to pipe section 150. In this mode, all fluid that passes through the heat generating device 108 is circulated to the fluid storage tank 110 and back to the heat generating device 108 with no flow leaving or entering the heat generation loop 102 through the heat dissipation loop 104 via pipe sections 150 and 158. The non-mixing configuration can be utilized for initial warm-up of the system and to protect the heat generating device 108 from undesirably low entering fluid temperatures.

Referring to FIG. 3, the hydronic system is shown as being in a mixing configuration wherein the mixing control valve 106 is at least partially open to the pipe section 150. In this mode, fluid flows from piping section 126 in the heat generation loop 102 into pipe section 150 of the heat dissipation loop. If the flow through pipe section 150 is less than the flow rate of the circulating pump 146, then the remaining flow is made up by fluid returning from the return manifold 140 via pipe sections 156 and 160. Also, the flow from pipe section 156 into pipe section 158 that returns fluid from the return manifold 140 to the heat generation loop 102 will necessarily be equal to the flow through pipe section 150. As stated previously, the mixing configuration can be utilized to maintain a temperature setpoint of the heat dissipation loop, such as the supply temperature to the supply manifold 138. The mixing configuration can also be utilized to ensure that a minimum temperature in the heat generation loop, such as the heat generating device 108 entering fluid temperature setpoint, is maintained.

Referring to FIG. 1, a fuel delivery system 134 is schematically shown that includes a tank, a fuel line, and a fuel pump for delivering fuel to an electric generator 162, such as an internal combustion engine, and to the burner 112. The electric generator 162 provides power to the heat generating device 108, the pumps 122, 146, and to the controller 50 (discussed later) and related components. In one embodiment, the fuel pump of the fuel delivery system 134 is configured to deliver about 1.2 gallons per hour (gph) to the electric generator 162 and up to about 4.3 gph to the burner 112. In one embodiment, a containment box 164 is provided on the ground surface heater 10 that is configured to capture liquid in the event of a leak in the fuel system or in the hydronic system. In one embodiment, the containment box 164 has a holding volume that is at least equal to the volume of fluid stored by the mobile ground surface heater 10. For example, the containment box 164 can be configured to have 100% of the stored fluid volume. Thus, in the event of a leak, the containment box operates to prevent contamination of the surrounding area.

Referring to FIGS. 5-8, a physical configuration of a mobile ground surface heater 10 utilizing the hydronic heating system 100 is shown. As shown, the ground surface heater 10 includes a chassis 170 to which a trailer hitch 166 and four wheels 168 are operably connected. The mobile ground surface heater 10 also includes a hose reel 172 for storing the conduits 142 when not in use. In one embodiment, the hose reel 172 is configured to store six 500 foot sections of flexible hoses 142. As such, the ground surface heater 10 may be easily transported to and from a work site with all necessary equipment by a vehicle. A shown in Table 1 below, the mobile ground surface heater may be provided in a variety of sizes and capacities.

TABLE 1 System Hose Hydronic Length Platform Engine Engine Engine Burner Fuel MAX Flow Max (Typical) Size HP RPM's Liter Rate (GPH) HOSE PSI (GPM) CFM's FT Mule 18 1800 1.5 2.1 40 15 1500 1500 Small 18 1800 1.5 4.3 40 25 4000 300

Control System

Referring to FIG. 4, the mobile ground surface heater may also include an electronic controller 50. The electronic controller 50 is schematically shown as including a processor 50A and a non-transient storage medium or memory 50B, such as RAM, flash drive or a hard drive. Memory 50B is for storing executable code, the operating parameters, and the input from the operator user interface 52 while processor 50A is for executing the code. The electronic controller is also shown as including a transmitting/receiving device 50C, such as a 3G or 4G network enabled communication device, for remote two-way communication. A user interface 52 may be provided to activate and deactivate the system, allow a user to manipulate certain settings or inputs to the controller 50, and to view information about the system operation.

The electronic controller 50 typically includes at least some form of memory 50B. Examples of memory 50B include computer readable media. Computer readable media includes any available media that can be accessed by the processor 50A. By way of example, computer readable media include computer readable storage media and computer readable communication media.

Computer readable storage media includes volatile and nonvolatile, removable and non-removable media implemented in any device configured to store information such as computer readable instructions, data structures, program modules or other data. Computer readable storage media includes, but is not limited to, random access memory, read only memory, electrically erasable programmable read only memory, flash memory or other memory technology, compact disc read only memory, digital versatile disks or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store the desired information and that can be accessed by the processor 50A.

Computer readable communication media typically embodies computer readable instructions, data structures, program modules or other data in a modulated data signal such as a carrier wave or other transport mechanism and includes any information delivery media. The term “modulated data signal” refers to a signal that has one or more of its characteristics set or changed in such a manner as to encode information in the signal. By way of example, computer readable communication media includes wired media such as a wired network or direct-wired connection, and wireless media such as acoustic, radio frequency, infrared, and other wireless media. Combinations of any of the above are also included within the scope of computer readable media.

Electronic controller 50 is also shown as having a number of inputs and outputs that may be used for implementing the operation of the mobile ground surface heater 10. For example, the electronic controller provides an output 122 a to activate and deactivate pump 122 and provides another output 146 a to activate and deactivate the circulating pump 146. Another output 106 a is provided to control the position of the mixing control valve 106. Yet another output 110 a is provided to the burner 112 to control the heating output of the heat generating device 108. It is noted that the output signal 110 a can be a modulating signal where a modulating burner is provided. Furthermore, where variable speed drives are provided for the pumps 122, 146, the corresponding output signals 122 a, 146 a may also be modulating or varying in nature.

The heat generating device 108 is also shown as having a number of related inputs for heating output and safety control. One input is a temperature sensor T1 that is used by the controller 50 to provide closed loop control of the output 110 a to the burner 112. Thus, the controller 50 can be configured to command the burner 112 to fire as required to meet a temperature setpoint, as measured at sensor T1. The heat generating device 108 can also be provided with a low water cut-off switch S1. The low water cut-off switch S1 shuts the burner off in the event that the water heater runs low on water, which could lead to damage to the water heater. The switch S1 may either be an input to the controller 50 which then shuts off the burner 112 and/or can be hard wired to the burner 112 such that no action by the controller 50 is required in order for a safety shutdown to occur. In any event, when the low water cut-off switch is activated, the burner 112 and pumps 122, 146 are commanded off and the system is shut down until reset.

The fluid storage tank 110 is shown as being provided with a float switch S2 that can be used as an additional input to shut the ground surface heater 10 off in the event of a loss of fluid. The float switch S2 can be set to ensure that a minimum fluid level is maintained in the fluid storage tank 110 and protects the hydronic heating system 100 from overheating the fluid. Also attached to the fluid storage tank 110 is a hydronic temperature sensor T2 that sends the water temperature to the controller 50. The temperature sensed at sensor T2 can be used as an input for the control of the mixing control valve 106 such that a minimum heat generation loop 102 temperature is maintained by the mixing control valve 106. As the temperature of the fluid in the fluid storage tank 110 is generally equal to the entering fluid temperature at the heat generating device 108, the sensor T2 and the mixing control valve 106 can thus be utilized to eliminate temperature shock to the heat generating device 108. Temperature shock, in a fuel fired heater, occurs when the fluid temperature returning to the heater is below 140° F. and causes the combustion gases to condense due to excessive cooling of the gases. This can shorten the life of the water heater. In one embodiment, the minimum temperature setpoint at sensor T2 is hard coded into the controller 50 to an extent that a user cannot operate the system below this setting.

Downstream of the mixing control valve 106, a supply loop temperature sensor T3 is provided that serves as an additional input to the controller 50. The temperature sensed at sensor T3 can also be used as an input for the mixing control valve 106. Where the minimum water temperature at T2 is satisfied, the mixing control valve 106 can be controlled to maintain a supply fluid temperature setpoint at sensor T3 thereby setting the desired water temperature to the conduits 142 hoses. As shown, the user interface 52 allows a user to set the supply fluid temperature setpoint and also provides an indication of the current temperature, as sensed at sensor T3. In one embodiment, the user interface 52 allows a user to select a setpoint anywhere between about 60° F. and about 190° F. Other ranges are also possible. Also, a pressure sensor P1 may be provided at the supply manifold 138 to ensure that over-pressurization does not occur, for example if bypass valve 148 fails to operate correctly. In such an instance, the controller 50 can shut the system down thereby preventing potential damage to circulating pump 146 and other system components.

In one embodiment, a ground temperature sensor T4 can be provided to serve as an additional input to the controller 50. The temperature sensor can be placed on the surface 12 or can be a probe sensor that is inserted through and extending beneath the surface 12. In some circumstances, the mobile ground surface heater 10 may be operated at a location without regular supervision. Where this is the case, the controller can monitor the ground temperature at sensor T4, and then either shut the system down or place the system in a maintenance mode once a user defined threshold, which may be an input at the user interface 52, has been reached. Furthermore, the controller 50 may communicate that the ground surface is at an acceptable temperature with transmitting/receiving device 50C to the operator, for example by short message service (SMS) text messaging. By shutting down or placing the ground surface heater 10 in a maintenance mode once the threshold ground/surface temperature has been met, the ground surface heater 10 can provide significant operating savings over those systems that run continuously without regard to the actual ground/surface temperature. Furthermore, by providing for remote communication, work crew scheduling can be more easily accomplished.

The controller 50 is also in communication with the fuel delivery system 134 in that the fuel tank is equipped with a fuel level sensor F2, which may be a float switch that allows the controller 50 to display the amount of fuel in the machine. This input also allows the controller 50 to shut the machine down, including the electric generator 162, heat generating device 108, and pumps 122, 146, before the ground surface heater 10 runs out of fuel preventing the operator from having to re-prime the fuel system. Additionally, a containment switch S3 may also be provided in the mobile ground surface heater 10 within the containment box 164. The containment switch may be a liquid sensor or may be a float-type switch. As leaking fuel can be extremely hazardous, the switch will deactivate all equipment associated with the ground surface heater 10 if a certain level of fluid is captured within the containment box 164. In the event of a system shutdown for any reason, the controller 50 may provide an indication at the user interface 52 and may also transmit a message to the user via transmitting/receiving device 50C.

Method of Operation

Referring to FIGS. 9-11, various operational modes of the system are shown. In a first process 1000, a method for operating a ground surface heater is also described. In one step of the method 1002, a ground surface heater having a heat generation piping loop and a heat dissipation piping loop are provided wherein the heat dissipation loop includes at least one heat transfer conduit. In another step 1004, a control valve is provided to provide a mixed flow to the heat transfer conduit by mixing heated fluid from the heat generation piping loop with return fluid from the heat transfer conduit. In another step 1006, the control valve operates to maintain a heat generation loop minimum temperature setpoint. In another step 1008, the control valve operates to maintain a heat dissipation loop temperature setpoint.

In one configuration, as shown at process 1100 on FIG. 10, the system gives priority to the heat generation loop minimum temperature setpoint over the heat dissipation loop temperature setpoint. At a step 1102, a command to initiate system operation is received. In a step 1104, the system is activated, including the generator, heat generating device, and the pumps. In a step 1106, the controller evaluates if the heat generation loop temperature (e.g. temperature at storage tank) is at or above a minimum temperature threshold. Where the heat generation loop temperature is below the threshold, the mixing control valve is modulated or otherwise controlled to shut water flow to the heat dissipation loop from the heat generation loop at a step 1108. This loop between steps 1106 and 1108 will continue until the heat generation loop is at or above the threshold temperature. Such an operation would be typical at system start-up or in a warm-up mode when all of the fluid in the system is initially at a low temperature. Once the heat generation loop temperature is satisfied, the mixing control valve is modulated or otherwise controlled at step 1110 to maintain the heat dissipation loop supply temperature setpoint. At a step 1112, the heat generation loop temperature is continuously monitored to ensure that the mixing control valve switches to satisfy the heat regeneration loop minimum temperature requirement, if necessary.

Referring to FIG. 11, a process 1200 that may be used in conjunction with processes 1000 and 1100 is shown wherein a ground temperature sensor is utilized to monitor heating progress. In a step 1202, the system monitors a ground temperature threshold which is periodically checked after a delay step 1204, or continuously monitored without a delay. Once the ground temperature has exceeded the threshold temperature, the system is commanded into a maintenance mode at step 1206. The maintenance mode may include cycling the entire system on and off, resetting the heat dissipation loop temperature setpoint, cycling the heat dissipation loop pump, and/or any other reduced energy input strategy to maintain the ground temperature at the threshold setting. At a step 1208, a notification is sent by the controller to a user that the heating operation has been completed.

The various embodiments described above are provided by way of illustration only and should not be construed to limit the claims attached hereto. Those skilled in the art will readily recognize various modifications and changes that may be made without following the example embodiments and applications illustrated and described herein, and without departing from the true spirit and scope of the disclosure. 

It is claimed:
 1. A mobile surface heater comprising: a. a heat generation loop including a heat generating device, a fluid storage tank, and a first pump for circulating a fluid through the heat generating device and the fluid storage tank; b. a heat dissipation loop in fluid communication with the heat generation loop, the heat dissipation loop including: i. a surface heating system having at least one heat transfer conduit extending between a supply manifold and a return manifold; ii. a second pump configured to circulate the fluid through the heat dissipation loop; and iii. a control valve configured to deliver a mixed fluid flow stream to the surface heating system by selectively mixing fluid from the heat generation loop with fluid returning from the surface heating system return manifold; c. an electronic controller configured to operate the mixing valve to maintain a temperature setpoint of the mixed fluid flow stream and to maintain a minimum entering fluid temperature setpoint of the heat generating device; and d. a chassis having at least one pair of wheels and supporting the heat generation loop and the heat dissipation loop.
 2. The mobile surface heater of claim 1, wherein the electronic controller includes a user interface configured to allow a user to select the mixed fluid stream temperature setpoint.
 3. The mobile surface heater of claim 1, wherein the electronic controller is configured to ensure that the minimum entering fluid temperature setpoint is satisfied before maintaining the mixed fluid stream temperature setpoint.
 4. The mobile surface heater of claim 1, further comprising a temperature sensor for monitoring a surface or ground temperature to be heated by the mobile surface heater.
 5. The mobile surface heater of claim 4, wherein the controller is configured to operate the system to maintain a surface or ground temperature setpoint once a threshold temperature of the surface or ground has been attained.
 6. The mobile surface heater of claim 5, further comprising a containment box for capturing leaked fluid.
 7. The mobile surface heater of claim 6, further comprising a liquid sensor for detecting a leaked fluid in the containment box wherein the controller is configured to deactivate the mobile surface heater when the leaked fluid is sensed.
 8. The mobile surface heater of claim 1, further including a safety bypass valve extending between the supply and return manifolds.
 9. The mobile surface heater of claim 1, wherein the heat generating device is an atmospheric water heater having a fuel fired burner.
 10. The mobile surface heater of claim 1, further comprising a generator for providing power to the heat generating device and the first and second pumps.
 11. The mobile surface heater of claim 1, wherein the control valve is a modulating three-way control valve.
 12. The mobile surface heater of claim 1, wherein the heat dissipation loop is connected to the heat generation loop at a location between the heat generating device and the fluid storage tank.
 13. A mobile ground surface heater comprising: a. a heat generation loop including: i. a first hydronic piping loop; ii. an atmospheric water heater in fluid communication with the first hydronic piping loop; iii. a storage tank connected to the first hydronic piping loop; and iv. a primary pump configured to circulate fluid through the heat generation loop; b. a heat dissipation loop including: i. a second hydronic piping loop in fluid communication with the first hydronic piping loop; ii. a ground heating system connected to the secondary hydronic piping loop including a supply manifold, a return manifold, and at least one flexible conduit configured to be placed on a ground location for heating; iii. a control valve configured to deliver a mixed fluid flow stream to the ground heater supply manifold by selectively mix supply water from the atmospheric water heater with water returning from the ground heater return manifold; and iv. a secondary pump configured to circulate water through the secondary hydronic loop, the mixing valve, and the ground heater; c. an electronic controller configured to operate the mixing valve to maintain a temperature setpoint of the mixed water flow stream and to maintain a minimum entering water temperature setpoint of the atmospheric water heater; and d. a chassis having at least one pair of wheels and supporting the heat generation loop and heat dissipation loop.
 14. The mobile ground surface heater of claim 13, wherein the electronic controller includes a user interface configured to allow a user to select the mixed fluid stream temperature setpoint.
 15. The mobile ground surface heater of claim 13, wherein the electronic controller is configured to ensure that the minimum entering fluid temperature setpoint is satisfied before maintaining the mixed fluid stream temperature setpoint.
 16. The mobile ground surface heater of claim 13, further comprising a temperature sensor for monitoring a surface or ground temperature to be heated by the mobile surface heater.
 17. The mobile ground surface heater of claim 16, wherein the controller is configured to operate the system to maintain a surface or ground temperature setpoint once a threshold temperature of the surface or ground has been attained.
 18. A method for heating a surface, the method comprising: a. providing a surface heater having a heat generation piping loop and a heat dissipation piping loop wherein the heat dissipation loop includes at least one heat transfer conduit; b. providing a control valve to provide a mixed flow to the heat transfer conduit by mixing heated fluid from the heat generation piping loop with return fluid from the heat transfer conduit; c. selectively operating the control valve to maintain a heat generation loop minimum temperature setpoint; and d. selectively operating the control valve to maintain a heat dissipation loop temperature setpoint.
 19. The method for heating a surface of claim 18, wherein the control valve is operated to give priority to the heat generation loop minimum temperature setpoint over the heat dissipation loop temperature setpoint.
 20. The method for heating a surface of claim 19, further including the steps of: a. monitoring a ground or surface temperature b. comparing the ground or surface temperature to a threshold value; and c. placing the surface heater in a maintenance mode once the ground or surface temperature has met or exceeded the threshold value such that the surface heater operates to maintain a ground or surface temperature at the threshold value. 